(SIGAR-150) Wrapper class to synchronize Sigar method invocation

Signed-off-by: Doug MacEachern <dougm@hyperic.com>

bindings/java/src/org/hyperic/sigar/Humidor.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) [2004-2009], Hyperic, Inc.
+ * This file is part of SIGAR.
+ * 
+ * SIGAR is free software; you can redistribute it and/or modify
+ * it under the terms version 2 of the GNU General Public License as
+ * published by the Free Software Foundation. This program is distributed
+ * in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
+ * even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA.
+ */
+
+package org.hyperic.sigar;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
+/**
+ * The Humidor provides access to a single Sigar instance.  Sigar has a
+ * high-cost setup/teardown and has a high amount of caching, used to determine
+ * things like the % of CPU used in-between calls.
+ *
+ * The Humidor also synchronizes access to all Sigar methods, so all
+ * calls will be serialized.
+ */
+public class Humidor {
+    private static final Humidor INSTANCE = new Humidor();
+    private Object LOCK = new Object();
+    private InvocationHandler _handler;
+    private SigarProxy _sigar;
+
+    private Humidor() {}
+
+    private static class MyHandler implements InvocationHandler {
+        private SigarProxy _sigar;
+        private Object _lock = new Object();
+
+        public MyHandler(SigarProxy sigar) {
+            _sigar = sigar;
+        }
+
+        public Object invoke(Object proxy, Method meth, Object[] args)
+            throws Throwable
+        {
+            try {
+                synchronized (_lock) {
+                    return meth.invoke(_sigar, args);
+                }
+            } catch(InvocationTargetException e) {
+                throw e.getTargetException();
+            }
+        }
+    }
+
+    public SigarProxy getSigar() {
+        synchronized(LOCK) {
+            if (_sigar == null) {
+                Sigar s = new Sigar();
+                _handler = new MyHandler(s);
+                _sigar = (SigarProxy)
+                    Proxy.newProxyInstance(Humidor.class.getClassLoader(),
+                                           new Class[] { SigarProxy.class },
+                                           _handler);
+            }
+            return _sigar;
+        }
+    }
+
+    public static Humidor getInstance() {
+        return INSTANCE;
+    }
+}